You can made a custom cable where 3 pins are used for the AES/EBU audio input and other two pins are used for the comms of your actual system.
I hope it is that simple. Today I use an old-fashioned comms cable with two wires spliced to BNC which also carries commands from a network-to-serial adapter plugged into the 568.2mm RS232 port. Would this adapter connect directly to Cat8, without any M electronics, to send commands?
When I look at RS232 pin assignments, I see more than Tx and Rx: Data Carrier, Set, Ready, Clear etc. and am over my head in understanding how to proceed so that I can sell or redeploy my old surround unit.